Outspoken agent Mino Raiola claims Pep Guardiola does not have the guts to sit with him and labelled the Manchester City coach's philosophy as "boring".
Raiola has previously taken aim at Guardiola for what he perceives to be poor treatment of his client Zlatan Ibrahimovic when the pair worked together at Barcelona.
Guardiola and Ibrahimovic are now on the opposite sides of the Manchester divide in the Premier League, with the two set to meet when United host City at Old Trafford on Saturday.
And Raiola, speaking to Cadena Cope, once more aimed a dig at former Bayern Munich coach Guardiola.
"I don't like him. I do not hate him, but I do not like him," he said. "Everyone knows what happened to Zlatan in Barcelona.
"He's a good coach but his football philosophy seems boring to me. He doesn't have the guts to sit next to me."
Raiola also insists he has "neither a good nor a bad relationship" with Real Madrid president Florentino Perez.
Paul Pogba, another client of Raiola's, was thought to be a target for Madrid before his world-record move to Manchester United, with Perez's reported poor relationship with Raiola said to have been a stumbling block.
But Raiola added: "I don't have a bad relationship with Florentino Perez. Actually, I have no relationship with him, I never talk to him.
"I do not need to be a friend or a foe with Florentino. With him I have neither a good nor a bad relationship."